I do remember a major scandal that occurred in the 1980's when somebody posted an advertisement to usenet. At the time, there was a lot of online discussion about why this was prohibited. I looked this up, and found that the internet backbone (the NSFNET) was funded by the NSF, who enforced an acceptable-use policy, prohibiting Backbone use for purposes “not in support of research and education.” [https://dl.acm.org/doi/pdf/10.1145/253671.253741]
So yes, it's possible, because we already did it once.
When we talk about banning ads, we tend to underestimate the power of capitalism and consumerism, while overestimating how much people truly value the privacy of their online privacy.